Advection of Particulates to/from Cells

If one or more Solids are suspended in a Fluid, the fluid concentration that is output is computed as the effective concentration, which includes the species The chemical (or non-chemical, such as bacterial or viral) constituents that are stored and transported through an environmental system in a contaminant transport model. In GoldSim, the Species element defines all of the contaminant species being simulated (and their properties). mass associated with the suspended Solids.

Note that when a suspended Solid is present in a Cell, an additional output is created called Dissolved_Conc_in_Fluid, where Fluid is the Fluid in which the Solid is dissolved (typically water). This output provides the actual concentration of dissolved species in the Fluid. The Concentration_in_Fluid output provides the effective concentration of species in the Fluid (accounting for species sorbed onto suspended solids).

Advective mass flux links involving Fluids containing suspended Solids transport both the species mass dissolved in the fluid and the species mass associated with (partitioned onto) the suspended Solid(s).

With regard to the transport of species mass on particulates from Cells, the following rules are followed:

• If the advective mass flux link A mass flux link in which a quantity of a medium is specified to flow from one pathway to another, carrying dissolved, sorbed, and/or suspended species with it. is between two Cells, then the particulates are only advected into the downstream (Inflow) Cell if the Solid exists in that Cell. (The Solid does not have to be specified as being suspended in the Inflow Cell, but it must exist in that Cell.) If it does not, GoldSim assumes that the Solid particulates are "filtered" out before entering the Inflow Cell (and remain in the Outflow Cell).
• If the advective mass flux link An interconnnection between two transport pathways that defines the rate at which species move between the pathways. is between a Cell and any other type of pathway, the particulates are always transported with the flowing fluid.
• If the Solid is not suspended in the Inflow Cell (or the Inflow pathway is not a Cell), conceptually, the particulates are assumed to immediately disintegrate upon entering the Inflow pathway, with the species mass which was associated with them instantaneously partitioning among the available media Materials (such as water, sand, clay, air) that constitute (are contained within) transport pathways. GoldSim provides two types of elements for defining media: Fluids and Solids. in the pathway.
• The Solid's Advective Velocity Multiplier (an Advanced property of the Solid medium) can increase the mass flux associated with the suspended Solid. The Advective Velocity Multiplier effectively controls the velocity (and hence the mass flux) of the advected particulate Solid relative to the advecting Fluid. The default value is 1 (it moves at the same velocity as the Fluid). But you can choose to have the suspended Solid move faster or slower than the Fluid.

• For computational reasons, the mass in a Cell in excess of the saturation capacity (the "precipitated" mass) is assumed to be precipitated only onto those Solids which are not suspended. Hence, although species mass can be partitioned onto (and transported with) particulate Solids, precipitated species mass is never associated with suspended Solids.

As is the case for the advecting Fluid itself, GoldSim uses the advective flux only to transport species mass and does not keep track of the movement of the suspended Solid media through the pathway network. That is, the advective flux has no effect on the quantity of the suspended Solid present in either the Outflow or Inflow Cell.